The present invention relates generally to head-up displays, and more particularly, to a helmet visor display that incorporates reflective, refractive and diffractive optical elements.
A typical conventional helmet visor display has three modules that include a combiner that acts as an eyepiece, a relay lens, and an image source generator. Three drawbacks are generally associated with the conventional helmet visor display: the relay lens is too complicated, the moment of inertia of the display is too large, and the pupil size is too small. Consequently, the conventional helmet visor display is relatively expensive to construct and is not comfortable to wear for long periods of time.
One conventional helmet visor display is disclosed in U.S. Pat. No. 3,940,204 entitled "Optical Display Systems Utilizing Holographic Lenses", issued to Withrington, and assigned to the assignee of the present invention. This optical display system includes three modules: one combiner, one relay module, and one image source generator module such as a cathode ray tube (CRT). Information displayed on the CRT is relayed by the relay module to form an intermediate image and then collimated by the combiner to generate an image at a comfortable position in front of a viewer. The optical design form of this helmet visor display system has several advantages. The relay module allows the size of the image generator to be small, and the combiner relays the eye pupil inside the relay module. Therefore, the size of the relay group is kept small.
However, there are several drawbacks associated with this conventional helmet visor display systems. The operating spectral bandwidth is somewhat narrow, the relay group is relatively complicated, the helmet visor display is relatively heavy, the moment of inertia is large, and the pupil size is relatively small. Consequently, conventional helmet visor displays are generally unconfortable for users to wear for a long period of time.
The conventional high image quality helmet visor display optical system is generally very bulky and extremely expensive. The moment of inertia of the visor is also very large. Therefore, the user is very stressed and uncomfortable and unable to wear it for an extended period of time. In typical applications for helmet visor displays, such as for aircraft, simulators, and medical systems, for example, the availability of lightweight, low cost, and low center of gravity helmet visor displays are very critical. Unfortunately, conventional helmet visor displays available today cannot meet all these requirements.
Therefore, it is an objective of the present invention to provide an improved helmet visor display that incorporates reflective, refractive and diffractive optical elements, and that substantially eliminates the problems associated with conventional helmet visor displays outlined above.